Huntington's Disease - An Overview
Huntington's Disease is a devastating and progressive neurological disorder that resu lts primarily from degeneration of nerve cells deep in the center of the brain. The condition was first described by George Huntington, a physician in New York, in 1872. Even then, the physician recognized the all-encompassing factors of the disorder when describing it as, "coming on gradually but surely, increasing by degrees, and often occupying years in its development until the hapless sufferer is but a quivering wreck of his former self".
The three most profound behavioral problems in Huntington 's disease come from the uncontrollable movements called "chorea," dementia, and the altered perception of the world. The course of Huntington's Disease can last anywhere from ten to 30 years from onset to death. The symptoms of HD usually develop when th e person is between the ages of 30 - 50 years, although they have been known to occur as young as two and as old as 70. It affects all races and ethnic groups and occurs with the same frequency in both men and women.
As the disease progresses, the se verity of the symptoms increase and can be divided into three stages. The first stage is characterized by subtle and slight uncontrollable muscular movements, including stumbling and clumsiness, lack of concentration and short-term memory lapses, and depr ession and changes of mood. In the middle of the disease's course, patients may need assistance with some daily activities because walking, speech and swallowing abilities deteriorate. Involuntary movements become more pronounced and may be noticeable to the casual observer. In the latter stages, patients with HD require full-time care, and often families opt to place their loved ones in nursing homes. Patients may no longer be able to speak or talk; rigidity may now be more of a problem than involuntary movements; feeding tubes often have to be used because patients can no longer swallow. However, even as the disease progresses, people with the disorder almost always recognize their families, are aware of the situation, and have the ability to understand . Death usually occurs by aspiration pneumonia, malnutrition, or heart failure.
At present, there is no cure for the disease, but dynamic progress has been made as researchers explore this illness. HD is inherited as an autosomal dominant condition. In March 1993, scientists realized that HD is caused by a mutation in a gene located on chromosome 4. This gene has a unique genetic sequence for CAG (cytosine-adenine-guanine) and codes for the amino acid glutamine, a building block for the huntingtin pr otein. Normal individuals have this sequence duplicated from 11 to 40 times in their genetic coding without having symptoms of HD. However, individuals with the disease have from 40 up to 100 repeated CAG segments. Juvenile Huntington's Disease occurs wit h 60 or more repeats, linking the longer chains of CAG sequences to...